In the construction of road beds, buildings, dams, irrigation systems, storm sewers, and other structures, one needs earth material aggregate of certain preselected sizes and shapes. The aggregate may, for example, comprise asphalt plant mix aggregate and fines, highway seal chips, terazzo materials, marble, quartz, silica, perlite, ores and concrete sand. In producing concrete it is often desirable or necessary to use earth material aggregate mixed with cementous substances. This aggregate frequently comprises broken rock or stones of an undesirably large size and/or shape, considering the use to which the concrete is to be put. Typically, the aggregate comprises pieces of rock too large for the intended use, as determined by industry standards. Because large pieces of rock more readily available and inexpensively obtainable in nature are cheaper and usually in greater supply than smaller pieces which, for example, are more suitable in most forms of concrete, it is frequently desirable and sometimes necessary to break down earth material aggregate of an available size into pieces of a preselected smaller size or sizes with a secondary crusher. Many times it is most convenient to be able to do this on the job rather than at some distant permanent site at which a non-portable secondary crusher must be located. Hence, it is desirable to have an efficient, portable secondary crusher of reasonable production capability and high reliability for use at job sites.
Portable secondary earth material crushers, because of weight, size and power limitations forced upon them by the necessity for portability have not proven to be as reliable as the construction industry would like. It has been found that most prior art portable or secondary crushers of earth materials are unsatisfactory in accordance with what the construction industry wants. One reason is largely because critical parts in prior art devices rapidly wear out. This means such devices experience large down time, and require much expensive maintenance. Some prior art devices do not produce a sufficiently cubical aggregate to meet engineering standards, but produce flattened aggregate which must be mixed with very high quality cubical aggregate in order to provide a mix capable of meeting industry standards. Lack of output capacity in such secondary devices is also a problem. From the above information, it can be readily seen that the construction industry and hence the public would greatly benefit from a decided advance in the secondary crusher art.
One object of the present invention is to provide efficient secondary earth material aggregate crushing at a reasonable output rate and at costs per unit or ton considerably less than previously known in the art of secondary crushing.
Another object of the instant invention is to provide reliable on-site secondary earth material aggregate crushing.
Still another object of the invention is to provide capability for selecting the size aggregate to be produced.
Yet another object of the invention is to produce a high quality cubical aggregate.
One advantage of the present invention is that a combined lubricating and cooling system therein continually flushes bearing surfaces.
Another advantage of the instant invention is the low maintenance required of an apparatus constructed in accordance therewith.
Yet another advantage of the instant invention is that in accordance therewith, vulnerable portions of the apparatus are protected from abrasion experienced in prior art devices.